The metabolism of inorganic pyrophosphate (PPi) will be studied relative to the pathogenesis of calcium pyrophosphate dihydrate (CPPD) crystal deposition disease (pseudogout); the origin of plasma PPi, the significance of a PPi-rich zone in deep articular cartilage compact bone, and intracellular PPi levels in cultured skin fibroblasts will be studied. The degree of saturation of joint fluids with PPi will be studied by incubation of such fluids with 45Ca - CPPD in vitro. Removal of CPPD from affected knee joints by lavage with Mg ions solutions will be attempted. The biological effects of IgG adsorbed to monosodium urate, silicon dioxide and CPPD crystals will be determined.